The invention relates to a drop-in probe for determining phase changes of a sample removed from a molten steel by thermal analysis, with a measurement head having an immersion end, in which is arranged a sample chamber having an inlet opening and a thermocouple projecting into the sample chamber with its hot solder joint and that has a cable bushing for signal cables of the thermocouple, wherein, on one end of the measurement head opposite the immersion end, the cable bushing emerges from this measurement head out of an outlet opening, and wherein a straight line between the immersion end and the outlet opening forms a longitudinal axis of the measurement head.
Such probes are known, for example, from U.S. Pat. No. 3,463,005. Here, a probe is described that is dropped into a molten metal from a great height on a signal cable. For stabilization, the measurement head has a paperboard tube on its end facing away from the immersion end, with the signal cable being guided through this tube. A thermocouple is arranged on the immersion end of the probe. An additional thermocouple is arranged on the side in a chamber formed of refractory material and is used for determining the liquidus curve. An additional drop-in probe is known from U.S. Pat. No. 4,881,824. It has, on its front end, a thermocouple as well as, on the side, a sample holding chamber. A similar drop-in probe is described in U.S. Pat. No. 5,275,488. For this probe, a thermocouple projecting from the measurement head is arranged on its immersion end. It is protected by metal braces that form a kind of cage on the immersion end of the probe.
Immersion probes that are immersed in the melt by means of a carrier tube that can be placed on a so-called lance are known, for example, from U.S. Pat. No. 4,842,418 or U.S. Pat. No. 5,577,841. The devices described there each have a sample chamber on their front end. Another immersion probe is described in German Patent DE 39 19 362 C2. Here, a sample chamber for measuring the liquidus temperature is arranged in a carrier tube. A sensor for determining the carbon content of molten metal in converter furnaces is known from Chinese published patent application CN 201041556 Y.